On Thu, Jan 19, 2006 at 02:13:50AM -0500, John Sowa wrote:
> I generally agree with Chris on technical issues, (01)
Ah, your wisdom knows no bounds, John! ;-) (02)
> but there are many unresolved practical issues about how to develop
> and use the technology. (03)
Sure 'nuff. (04)
> So I'll add more qualifications and comments to some of the points in
> this thread:
>
> CM> I prefer a nice, simple definition:
> >
> > An ontology is a set of sentences in a formal language.
>
> Yes, but. That says what it is, but it doesn't explain why anybody
> would want one or what they'd do with it. I would therefore add the
> following clause:
>
> "that is designed to characterize the entities of interest in some
> domain for the purpose of representing, storing, and communicating
> information about them and performing deductions and computations with
> that information." (05)
I'm afraid I have to disagree if you want to include this in the
*definition* of an ontology, as it turns a notion that is clear and
precise into one that is fuzzy and indeterminate. On my proposed
definition, there is always a definite answer, at least in principle, to
the question: Is this an ontology? With your proposed emendation,
before we can determine whether something is an ontology, we need to
figure out what it was designed for, and the hopelessly intentional
"designed for" relation is inherently neither precise nor determinate.
Hence, with your emendation, it will often be the case that there is no
definite answer to the question of whether something counts as an
ontology. (06)
However, your point is well taken; I simply think it has to do with the
important, but orthogonal, issues of quality and evaluation, not with
the more formal matter of *definition*. Thus, I think your point is
best made in accompanying *documentation*, wherein the simple
definition would be glossed immediately with: (07)
Typically, ontologies are designed to characterize the entities of
interest in some domain for the purpose of representing, storing, and
communicating information about them and performing deductions and
computations with that information. (08)
> >> What is the scope of an ontology?
> >
> CM> I don't know what "scope" means.
>
> I would say that it characterizes some domain of interest for some
> purpose, such as developing and supporting applications that can
> successfully use a significant amount of detailed information about
> the entities in that domain. (09)
Sure thing -- good documentation! :-) (010)
> >> Do they change over time?
> >
> CM> No. Though of course one can trace change through an
> > evolving series of ontologies.
>
> That is like asking whether a program changes over time. The answer
> may be "no", but version 1.0 is typically replaced by v. 1.1, 1.2,
> ..., 2.0, 2.1,.... (011)
Just so, exactly my point. (012)
> >> How big is an ontology? How small can it be?
>
> I agree with Chris that the size is somewhere between 0 and infinity,
> but for reasonable estimates, we should look at Cyc, which had about 2
> million axioms about 2 years ago, and may have acquired a few more
> since then. Most current ontologies are much smaller, but future
> versions are likely to be as big or bigger. (013)
Right. I was giving the theoretical upper and lower bounds. (014)
> I agree with Chris that an ontology is a theory, not a lattice. But
> it is possible to relate all the theories expressed in a particular
> version of logic in a lattice. Each node of the lattice would be a
> particular theory, and the theories could be related as
> generalizations, specializations, siblings, or distant cousins in the
> lattice. For more info about those issues, see
>
> http://www.jfsowa.com/logic/theories.htm (015)
Right, but theories are deductively closed on this approach, and I don't
think we should identify ontologies with theories in that sense, as, for
one thing, you can't distinguish between equivalent ontologies that use
different axioms. (016)
Frankly John, I don't see the point of talking about the "lattice of
theories" for a given language anyway. I think sometimes your talk of
the lattice suggests that it is itself something might be usefully
apprehended and studied. In general, however, there are uncountably
many theories in such a lattice, so we will never be able even to
apprehend one as an object of study except for the most technical and
abstract purposes. Typically, all that's *really* useful to us are the
possible logical relations that can hold between two *given* theories:
equivalence, subsumption, compatibility, inconsistency, inconsistent but
containing equivalent subtheories, etc. These relations of course would
all be "pictured" by the lattice, but, again, typically, we'll never
study the lattice per se, only specific nodes of interest and the
particular logical relations they bear to one another. (017)
So I guess my point is that, for the most part, I don't think anything
particularly useful is to be gained by talking about the lattice of
theories for a given language in the context of ontological engineering,
and that indeed it might engender more confusion than clarity. (018)
-chris (019)
-- (020)
Christopher Menzel # http://cmenzel.org
Philosophy, Texas A&M University # cmenzel@xxxxxxxx
College Station, TX 77843-4237 # 979.845.5660 (021)
_________________________________________________________________
Message Archives: http://colab.cim3.net/forum/ontac-dev/
To Post: mailto:ontac-dev@xxxxxxxxxxxxxx
Subscribe/Unsubscribe/Config: http://colab.cim3.net/mailman/listinfo/ontac-dev/
Shared Files: http://colab.cim3.net/file/work/SICoP/ontac/
Community Wiki:
http://colab.cim3.net/cgi-bin/wiki.pl?SICoP/OntologyTaxonomyCoordinatingWG (022)
|